1. Field of the Invention
This invention relates to a vehicular optical-radar apparatus, and particularly to a vehicular optical-radar apparatus utilized for other optical radar apparatuses.
2. Description of the Prior Art
In the present society, a demand for traffic safety has been increased. Particularly, a multi-vehicle collision or the like on an expressway tends to directly lead to a large traffic accident, and measures to prevent such an accident should be taken.
As a method for preventing accidents, a system has been proposed in which the distance to a vehicle ahead and the difference of speed therefrom are detected and calculated to transmit a danger signal to a driver.
In a conventional optical distance-measuring apparatus, as shown in FIGS. 12 and 13, light emitted from a light emitting portion 1 arranged within a lens-barrel 5 transmitted through a light emitting lens 3 and is then formed into an outgoing light Lt. The outgoing light Lt irradiates on a reflecting body, for example, a reflex reflector of an object of a distant vehicle ahead or the like and is formed into a reflected light Lr, which is condensed by a light receiving lens 4 and received by a light receiving portion 2 of the lens-barrel 5.
A beam spot 7 reflected in a screen 6 irradiated on the object is substantially circular as shown in FIG. 14. In this case, the distance between the light emitting portion 1 and the light receiving portion is D (see FIG. 13).
However, in the aforementioned prior art system, as the light emitting and light receiving lenses, circular lenses are used as they are in their shape without working. Therefore, the distance between optical centers of the light emitting portion 1 and the light receiving portion 2 is large. Accordingly, there arises a problem in that a quantity of reflected light (a quantity of receiving light) is reduced.
Further, the beam spot 7 irradiated on the object is circular as shown in FIG. 14, and unnecessary portions are present in upper and lower ends or the like. Accordingly, as shown in FIGS. 15 and 16, out of light irradiated on a reflecting body C, a portion in which an angle .theta.1 between an incident axis B and a reflected light F is large; that is, a less effective power portion is utilized. This causes a problem in that detection performance of the light receiving portion is deteriorated.
Moreover, the aforementioned optical distance-measuring apparatus for use with vehicles is insufficient in reliability such as precision. Further improvements have been required.
It is an object of the present invention to provide a vehicular optical-radar apparatus which can enhance the detetection performance of a light receiving portion and wherein unit assembly and mounting of the beam emitting and receiving portions to the vehicle are improved, while overcoming the problems noted above with respect to the prior art.